The present invention relates to archery equipment, and more particularly to an improved compound bow having a novel bowstring tensioning assembly that exhibits superior dropoff characteristics over existing conventional recurve and compound bows.
As is well known, conventional bows, such as a recurve bow, comprise a main body having oppositely extended arms, and a bowstring is attached to the free ends of the arms and is held under tension by the resilient action of the arms. In use, as the string is drawn back by an archer, the force required to draw the bowstring from its initial position to its drawn position increases with the distance it is drawn. To retain the bowstring in its drawn position thus requires a substantial amount of force, and is quite tiring to the archer who desires to hold the bow in its drawn position for any substantial amount of time, for example, when the archer is hunting. Compound bows have sought to solve this problem by reducing the effort required to maintain the bow in its drawn position. To accomplish this, a pair of cams or eccentric pulleys are rotatably mounted on the free ends of the bow arms with the bowstring attached to these cams. Once again, the resilient nature of the arms provides the force necessary to maintain tension on the bowstring, and the force to draw the bowstring increases as it is moved from its initial position through an intermediate position toward its fully drawn position. However, by providing cams or eccentric members, the cam members rotate immediately prior to reaching the fully drawn position. This reduces the force required to maintain the bowstring at its fully drawn position. Indeed, compound bows of the prior art have accomplished this dropoff characteristic to a degree that the force required to hold the bowstring fully drawn is approximately one half the maximum force during the drawing operation.
An archer must still employ a fairly powerful bow when hunting, however, and often the hunter requires a bow that has a drawing force on the order of sixty or more pounds. Thus, even a compound bow with a fifty percent dropoff characteristic requires a pull of thirty pounds or more to resist the release of the bowstring from its fully drawn position supporting an arrow for launching. In many cases, the hunter is required to hold the bowstring at its fully drawn position for periods up to two minutes while stalking game so that this can become quite tiring and indeed decrease the qccuracy of the archer due to fatigue despite the improvements of the compound bow over a conventional bow. A conventional recurve bow is naturally more tiring.
The dropoff characteristics of a bow can also affect the weight of an arrow that may be launched. It has long been known that an arrow must arch or fluctuate about its spine as it is launched and as it continues in flight in order to travel on a true path. An arrow which is light in weight typically will be more susceptible to fluctuation than a heavier arrow. Since too much fluctuation is undesirable, a bowstring that accelerates a lighter arrow too rapidly can introduce too much fluctuation so that a heavier arrow must be employed. For the same power of bow, then, this reduces the energy of the arrow since the energy is linearly proportional to the square of the velocity. By having a more gradual initial acceleration a lighter arrow may be used without causing over fluctuation, with this arrow attaining a greater velocity and thus an increased energy. Therefore, it is desirable that a bow have sufficient power but exhibit a dropoff that occurs more gradually to a level as low as possible in the fully drawn bowstring position.